A method for increasing the hafnium content in tantalum-tungsten alloy comprises: 1. Mixing tantalum powder, tungsten powder and hafnium powder evenly according to the design content to obtain a mixed powder; 2. Press the mixed powder into a blank strip; Third, the billet is sintered at high temperature under vacuum to obtain the sintered billet; Fourth, the sintered billet is smelted twice by vacuum electron beam to obtain tantalum tungsten alloy. While the raw material powder is pre-alloyed by high temperature vacuum sintering, argon gas is filled into the cooling process in time to effectively reduce the volatilization of hafnium, and different melting speeds are adopted in the two rapid vacuum electron beam melting processes to avoid a large amount of hafnium element being extracted, and at the same time to promote the homogenization of tantalum tungsten alloy to further avoid a large amount of volatilization of hafnium element. The final mass content of hafnium in tantalum tungsten alloy is more than 80% of the design content.
Tantalum alloy has the advantages of high melting point, high strength, good ductility at room temperature, corrosion resistance and easy machining. It is widely used in chemical industry, aviation, aerospace and atomic energy industry. At present, there are mainly Ta2.5W, Ta7.5W, Ta10W and Ta12W tantalum alloys in mature application in China, but these alloys all have the problem of non-oxidation resistance. By adding a certain amount of Hf element, the solubility of oxygen in the alloy can be effectively reduced, and the corrosion resistance of the alloy to alkali metals such as potassium, sodium, lithium, cesium and mercury can be improved. After adding Hf element, the high temperature performance and processing performance of the alloy are good, in the temperature range of -160 ℃ to 1370 ℃, the alloy maintains good ductility and strength, and can work in extreme environments such as ultra-high temperature, ultra-high pressure, high-speed airflow erosion, acute cooling and acute heating.
TaW series alloys have a high melting point and are easy to oxidize. They are generally prepared by vacuum electron beam melting and a small amount by powder metallurgy. The melting point of Hf is 2222℃, which is nearly 800℃ lower than the melting point of Ta, near the melting point of Hf, the vapor pressure of Hf is 3 orders of magnitude higher than that of tantalum, so Hf melts before Ta in vacuum melting, and is extremely volatile, so for TaWHf series alloys, the addition method of hafnium and the preparation method of the alloy will affect the final composition of the alloy. The United States uses the method of electron beam melting and electric arc furnace melting, the high melting point, difficult to volatilize Ta, W is alloyed with electron beam melting, and then Hf is added in electric arc furnace melting, combining the two melting methods, not only to achieve the purification effect of electron beam melting, but also to take advantage of the advantages of electric arc furnace rapid melting, to avoid the problem of uncontrollable volatilization of Hf elements.
